Using extensions of Prager's theories of optimal plastic design, slabs and grillages are optimized within various geometrical constraints ensuring simplicity and practicality. The two classes of problems considered are: (1) Grillages consisting of prismatic beams of preassigned directions and length but variable spacing and balanced prestressed elastic plates having tendons of preassigned directions terminated at the edges only; and (2) slabs with curtailed negative reinforcement of preassigned length. The results given represent rigorous analytical optima as well as identical upper and lower bounds on the limit load. A comprehensive set of solutions is tabulated for rectangular domains with various boundary conditions and the moment volumes for constrained geometry are compared graphically with absolute minimum volumes of unconstrained solutions. Finally, the most economic length of negative reinforcement is calculated for rectangular slabs.
Reaction rates between sulfide and oxygen in the presence of extraneous substances were studied. Divalent metal ions and organic substances such as phenols and aldehydes were found to exert accelerating effects. Compounds containing a basic nitrogen with a free electron pair were found to be chain-breakers and to inhibit the reaction. Four types of influence were observed in this study: (1) A shortening or lengthening of the induction period; (2) a change in the stoichiometry of the reaction; (3) a change in reaction rate; and (4) an induced oxidation of the added organic material. It is concluded that the treatment of sulfide-bearing industrial wastewater as well as the oxygenation of sulfide in natural environment can be greatly accelerated through proper use of catalysts.
A design approach for plastic media bio-oxidation towers is presented. This paper considers that the rate of mass transfer of oxygen is the rate controlling factor in the overall rate of reduction of BOD. A simplified mathematical model is presented which permits the prediction of the BOD removal which can be obtained in plastic media towers of a given size and loading. This model permits a design engineer to evaluate the capabilities of a proposed design, and it gives plant operators a guide for trouble-shooting plants with poor removals.
Agricultural runoff consists of nonpoint sources that range from almost natural runoff to that from concentrated agricultural operations such as animal feedlots and fertilized fields. Control of the latter is possible by waste management and land conservation techniques. Increases in agricultural efficiency have been associated with a variety of potential and real environmental problems. The paper attempts to quantify some pollution problems due to agricultural runoff and to put these problems in perspective. The major topical areas include erosion, animal feedlots, rural runoff, pollution characteristics, and effect of fertilizers. Management methods to control the quantity and pollutional quality of the runoff are noted. The paper stresses that agriculture should institute a systematic, coordinated approach for specific production operations to reduce excesses that could cause environmental degradation.
A series of bioassay experiments concerning the effects of heated water on white perch have shown that, for water temperatures ranging between 82°F (300.9°K) and 97°F (309.3°K), the lethal effects on a white perch being held at any temperature within that range will occur within the first 36 hrs of exposure. This is shorter than the time period prescribed in general by the standard bioassay procedure. Three parameters are given which more completely describe the pattern of mortality. Investigation has shown that: (1) A relationship exists between the temperature at which mortalities of the white perch are incipient and the temperature at which the body of the fish is functioning and (2) the lethal effects on white perch caused by extreme water temperatures are independent of the rate of temperature increase.
The purpose of this paper is to demonstrate, by means of a case study of water reuse, the usefulness of applying Kazanowski's cost-effectiveness approach to civil engineering systems. This method facilitates evaluating and comparing alternative systems designed to reach a given goal. The case study is concerned with two concurrent problems that are commonly facing metropolitan areas: securing an adequate water supply and disposing of the sewage effluent. Several distinct alternative systems to deal with these problems are identified, such as exchange for irrigation water, or tertiary treatment and recycling. For each alternative system, the economic analysis, the environmental impact upon implementation, and the horizontal and vertical externalities are evaluated and presented in tabular form. The result of a sensitivity analysis performed on major system variables is given.
Interrelationship of the numerous factors in waste management can be explored in a gaming environment. Management science aids can be introduced to guide the decision-making. An experimental game has been devised for use within IBM which implements these objectives. It is interactive, terminal-oriented, and programmed in APL. The scenario for the game treats the environmental area of solid-waste management. It is directed to players with minimal knowledge of management science. Techniques include shortest route, transportation, and maximal flow problems. More generally, the system which supports the game can be used to author other game scenarios. Features include interactive, natural language communication, and prompting.
